When an aircraft flies in cold, moist air, especially at low altitudes, ice can form rapidly, both on and behind the leading edge of the wing and other portion of the aircraft. Presence of ice can disturb the airflow and can radically alter the lift of the wings and the center of gravity of the aircraft. hence the handling characteristics thereof. This phenomenon has caused a number of fatal accidents and loss-of-control events. In order to alert the pilot or the aircraft operator, of the present of ice, one or more ice detectors are mounted on the wing and/or on the fuselage, and configured to indicate when ice is accumulating thereon. As a response the pilot can direct the aircraft away from the zone in which the ice is likely formed. FIG. 1 shows a prior art ice detector 10 mounted on a wing 8 of an aircraft 5. The ice detector 10 is configured to detect accumulation of ice on the wing 8. According to some examples the ice detector can be thermostat configured to detect the temperature thereon. According to other examples the ice detector can be an optical device configured to detect accumulation of ice, for instance, by detecting a change in refractive index. According to other examples, the detector can be an acoustic detector which is configured to detect changes in the sound wavelength when icing occurs. According to a further example the ice detector can include a radioactive source and a sensor for detecting the radioactive emission. The ice detector can detect changes in emission level when icing occurs between the radioactive source and the sensor.